The following patents and publications are believed to represent the current state of the art:
U.S. patents:
U.S. Pat. Nos. 5,969,855; 5,969,853; 5,936,253; 5,870,191; 5,814,815; 5,777,736; 5,751,475; 5,619,372; 5,600,440; 5,471,303; 5,446,540; 5,235,587; 5,159,474; 4,653,921; 4,407,569 and 4,190,366.
Other Patents:
JP 9230947 (Abstract); JP 9179029 (Abstract); JP 8094936 (Abstract); JP 7261089 (Abstract); JP 7225341 (Abstract); JP 6186504 (Abstract); EP 0555099; GB 2315700
Other Publications:
Phillion, D. W., “General methods for generating phase-shifting interferometry algorithms”—Applied Optics, Vol. 36, 8098 (1997);
Pluta, M., “Stray-light problem in phase contrast microscopy or toward highly sensitive phase contrast devices: a review”—Optical Engineering, Vol. 32, 3199 (1993);
Noda, T. and Kawata, S., “Separation of phase and absorption images in phase-contrast microscopy”—Journal of the Optical Society of America A, Vol. 9, 924 (1992);
Creath, K., “Phase measurement interferometry techniques”—Progress in Optics XXVI, 348 (1988);
Greivenkamp, J. E., “Generalized data reduction for heterodyne interferometry”—Optical Engineering, Vol. 23, 350 (1984);
Morgan, C. J., “Least-squares estimation in phase-measurement interferometry”—Optics Letters, Vol. 7, 368 (1982);
Golden, L. J., “Zernike test. 1: Analytical aspects”—Applied Optics, Vol. 16, 205 (1977);
Bruning, J. H., et al. “Digital wavefront measuring interferometer for testing optical surfaces and lenses”—Applied Optics, Vol. 13, 2693 (1974); and
Gerchberg, R. W. and Saxton, W. O., Optik 35, 237: (1972).